1. Field of the Invention
The present invention relates to a method and apparatus for managing power in a mobile communication system.
2. Background of the Prior Art
Generally, a cellular phone can be characterized as a mobile station, a mobile terminal, or a user device. A mobile terminal communicates with one or more base stations through an aerial interface. A base station is managed by a base station controller. In some systems, the base station controller functions as a radio network controller, and is hereinafter referred to as an RNC.
A radio network controller is typically a connection-oriented type, such as a PSTN (Public Switched Telephone Network) or an ISDN (Integrated Services Digital Network), and is connected to one or more communications networks through one or more control nodes. Control nodes can include a mobile switch center node for accessing a circuit-switched network, and a general packet radio service node for accessing to a packet-switched network.
An exemplary asynchronous mobile communication system is described with reference to FIG. 1. Referring to FIG. 1, an asynchronous mobile communication system includes a user equipment (UE) 100, an RNC 110, a node B 120, a base station modem 130, and a core network (CN) 140. The RNC 110 controls radio resources in the cell it is part of, and also functions to control a corresponding cell.
In addition, the RNC 110 sets minimum power value, maximum power value or the like of a corresponding call when an initial call is set in a mobile communication system. The RNC 110 transmits to the node B 120 a radio link setup command along with the set minimum/maximum power value contained in the setup command.
The node B 120 is a logic node that is responsible for radio transmission/receipt to or from the user equipment 100 that is located in one or more cells. The node B 120 constitutes a radio link in response to a radio link setup command transmitted from the RNC 110, and transmits to the base station modem 130, initial power value, minimum power value and maximum power value, with all of these values contained in the radio link setup command.
The base station modem 130 changes the down link power value between the minimum power value and the maximum power value transmitted from the node B 120 by the inner loop power control.
FIG. 2 is a flow diagram showing a power managing method in a related art mobile communication system. Referring to FIG. 2, user equipment (UE) transmits a radio resource control (RRC) access request command to the RNC so as to set a signal path. (S200) Here, the RRC access request command includes an identification number of the user equipment, a request service category requested by the user, and a measurement on random access channel (RACH) information element (MORIE).
The RNC receives an RSCP (Received signal code power) value or an Ec/No (i.e., RSCP/RSSI (Received signal strength indicator)) value from the MORIE contained in the RRC access request command. (S201). The RRC indicates the protocol layer managing the radio resource. The MORIE is an information element contained in the RRC access request command transmitted from the user equipment to the RNC. The MORIE may include information, such as Ec/No or RSCP, measured on the RACH by the user equipment. After the step of 201, the RNC obtains the down link initial power value from the RSCP or Ec/No value through the open loop power control. (S202)
After step S202, the RNC obtains the down link minimum power value and the down link maximum power value from the obtained down link initial power value. (S203)
After the step of S203, the RNC sets a radio link setup command including the obtained down link initial power value, the down link maximum power value, and the down link minimum power value. (S204). Other data may also be included in radio link setup command.
After the step of S204, the RNC transmits the set radio link setup command to the node B. (S205)
In step S205, the node B constitutes a radio link in response to the radio link setup command transmitted from the RNC, and then transmits to the base station modem down link initial power value, down link minimum power value and maximum power value, all of which are contained in the radio link setup command. (S206, S207). In step S207, a signal path of the user equipment is set. After this step, a traffic path of the user equipment is set.
Hereinafter, a method for setting the traffic path will be described. A core network transmits a RAB (Radio Access Bearer) allocation request command to the RNC, so as to set the traffic path. (S208). After the traffic path is set, the RNC resets the down link maximum power value and the down link minimum power value in response to QoS (Quality of Service) parameter of the RAB allocation request command. (S209) In other words, the RNC sets differently the down link maximum power value and the down link minimum power value according to a service quality level.
After the step of S209, the RNC inserts the reset down link maximum power value and the reset down link minimum power value into a radio link reconfiguration command, and then transmits the radio link reconfiguration command to the node B. (S210, S211). However, since the minimum power value and the maximum power value are not changed, there is no appropriate preparation for an instantaneous increase of power caused by an abrupt movement of a mobile terminal moving towards shadow areas within a communication sector. An additional problem is that the RNC must set sufficient minimum and maximum power ranges, when the minimum power value and the maximum power value are set.
Further, the down link initial power value and its range are fixed. In this case, since the terminal abruptly moves to shadow areas, the power magnitude required is instantaneously increased and instantaneous power of the base station modem is also rapidly increased, due to inner loop power control. This causes a problem of attenuating power occupiable or useable by other subscribers. Also, with an abrupt increase of down link power, up link power is also increased, thereby increasing interference, so that other subscriber's speech quality is degraded.
Furthermore, in third generation systems, instantaneous increase of power affects call admission control (CAC), so that the probability of admitting other subscribers is reduced.